Releasably locking dilator and sheath assembly

ABSTRACT

A releasably locking dilator and sheath assembly and methods for releasing the dilator from the sheath and longitudinally splitting the sheath. The assembly includes a dilator having a dilator hub and a sheath having a sheath hub. The sheath hub may have a valve and has two opposing winged tabs, each tab having a perpendicular portion and an angled portion as well as a female threaded portion. The dilator hub has a male threaded portion designed to engage the female threaded portion of the sheath hub. The dilator is released from the sheath by rotating the dilator 90° in relation to the sheath and pulling the dilator out of the sheath. The sheath is longitudinally split by creating a couple on each of the winged tabs thereby forcing the sheath and the sheath hub to split longitudinally. With the sheath and sheath hub split longitudinally, the sheath is removed from around a catheter while leaving the catheter in place.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of U.S. patent applicationSer. No. 12/165,896 filed Jul. 1, 2008, which is a Divisional of U.S.patent application Ser. No. 10/949,614 filed Sep. 24, 2004, which is aContinuation in Part of U.S. patent application Ser. No. 10/651,114filed on Aug. 28, 2003, which claims the benefit of U.S. ProvisionalPatent Application Ser. No. 60/406,740 filed on Aug. 29, 2002. Thedisclosures of these applications are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to invasive medical devices which aid in thecatheterization of human blood vessels. In particular, this inventionrelates to a releasably locking dilator and tear away sheath assembly,which is used to enlarge an opening in a patient's blood vessel duringinsertion of a catheter into the blood vessel and then guide thecatheter into the blood vessel to be catheterized.

BACKGROUND OF THE INVENTION

Catheters are used in numerous medical procedures. In particular,catheters are used for the introduction or removal of fluids fromvarious venous regions and vessels throughout the body, such as forhemodialysis. The procedure by which these catheters are introduced tothe body is delicate and complex. One particularly intricate challengeto catheterization is enlarging a hole in the flesh and vessel to becatheterized while minimizing blood loss and trauma to the patient.

Generally, to insert any catheter in a blood vessel, the vessel isidentified by aspiration with a long hollow needle in accordance withthe Seldinger technique. When blood enters a syringe attached to theneedle, indicating that the vessel has been found, a thin guide wire isthen introduced, typically through the syringe needle or otherintroducer device, into the interior of the vessel. The introducerdevice is then removed, leaving the guide wire within the vessel. Theguide wire projects beyond the surface of the skin.

At this point, several options are available to a physician for catheterplacement. The simplest option is to pass a catheter into the vesseldirectly over the guide wire. The guide wire is then removed. However,use of this technique is only possible in cases where the catheter is ofa relatively small diameter, made of a stiff material and notsignificantly larger than the guide wire. If, however, the catheter isof a relatively large diameter and/or not made of a soft material, onepreferable method of inserting the catheter into the vessel is throughan introducer sheath. The introducer sheath is simply a large, stiff,thin-walled tube, which serves as a temporary conduit for the catheterthat is being placed. The sheath is positioned by placing a dilator,which has a hollow passageway along its longitudinal axis, inside of thesheath and passing both the dilator and the sheath together into thevessel over the guide wire. The dilator expands the opening in the bloodvessel to allow for catheter insertion into the vessel. The guide wireand dilator are then removed, leaving the thin-walled sheath in place.The catheter is then inserted into the vessel through the sheath.

In a setting where a catheter with a hub or other attachment at theproximal end of the catheter has a feature which is larger than that ofthe inner diameter of the sheath, it is necessary to have a tear-awaysheath that can be split away from the catheter as the sheath is beingremoved from the patient. By splitting the sheath along its longitudinalaxis as the sheath is being removed from the patient, the insertingphysician will be able to pull out the sheath in such a way that theportion removed from the patient is split, thereby not interfering withany encumbrances on the catheter. Generally, tear away sheaths aremanufactured in a way that aids in the tearing of the sheath at twoopposing points on the circumference of the sheath, thereby splittingthe sheath into two halves separated longitudinally through the centerof the sheath.

A sheath is generally constructed with a hub at its proximal end. Thishub serves as a handle, a mating point for a dilator, and a flat surfaceto aid in the prevention of blood loss or contamination. When a sheathneeds to be split apart in order to be successfully withdrawn from thebody while leaving the catheter in place, the hub will also have to besplit apart in order to clear the catheter. Preferably, the hub willsplit along the same lines as the sheath. To accomplish this, the hubmust be designed with reveals or other weaknesses along two longitudinallines aligned with the weaknesses in the sheath. Some previous examplesof these weaknesses are tabs or webs which connect two halves of thehub, or recesses in the material comprising the hub. The weaknesses inthe hub will help the inserting physician to break apart the hub in linewith the tear seams on the sheath.

Another important facet of the hub is a set of tabs that protrude fromthe center. These tabs not only help the inserting physician to align,insert and withdraw the sheath, but also to pull the sheath so that thesheath can be removed from around a catheter while still leaving thecatheter in place. There are a number of different tab configurations,but it is important to have one which allows for easy maneuverability,control, and leverage. One design includes a hub wherein the tabsprotrude from the hub perpendicular to a plane which includes the tearseams in the sheath and the longitudinal axis of the sheath. In thisdesign, the tabs are diametrically opposed from each other and arespaced in such a way that when the tabs are grasped and pulled apartfrom each other, the sheath and its hub will split down the middle.Another desirable feature of the tabs is that the tabs provide leveragefor breaking apart the hub in a manner that does not cause trauma to theincision in the body.

During insertion, especially in the time between the removal of thedilator from the sheath and the insertion of the catheter through thesheath, it is possible for blood loss through the sheath, or theintroduction of contaminants or air through the sheath and into thevessel. For this reason, it is desirable that measures be taken toprevent blood, air or contaminants from traveling through the sheath. Inthe past, inserting physicians have simply held their thumb over theopening in the proximal end of the sheath; however, a more permanent andreliable means for preventing blood, air or contaminants from travelingthrough the sheath is desirable. It is therefore desirable for the hubto include a valve located in the sheath. Such a valve would facilitatethe insertion of objects such as a catheter, dilator or syringe throughthe sheath while restricting blood loss and reducing the chance ofcontaminants entering the patient's bloodstream when the sheath is notengaged with a dilator or a catheter.

In the case where a sheath does not have a small diameter or a narrowpoint, the dilator is often used to aid in the insertion of the sheath.The dilator has a long tubular section, the outside diameter of which isslightly smaller than the inside diameter of the sheath. The dilatoralso has a pointed tip on its distal end and a hollow center, which runsalong the entire length of the dilator. The dilator is inserted into thebody with the guidewire running through its center, thereby allowing thetip of the dilator to follow the guidewire to the place that is to becatheterized. On its proximal end, the dilator may have a hub. Like thehub of the sheath, this hub can also serve a number of purposes, such asproviding a stable handle to aid in guiding the dilator into the vein,and as a mechanism which can mate with the sheath hub to form a lockedconnection.

Some dilator and sheath assemblies that include a connection between thedilator and sheath are known. U.S. Pat. No. 5,885,217 to Gisselberg etal. discloses a dilator and sheath assembly, wherein the dilator andsheath are held together by locking tabs which provide a stop to holdthe dilator in place during insertion. However, in this configuration,the dilator may rotate about its longitudinal axis in relation to thesheath, thereby inadvertently and prematurely disengaging the dilatorfrom the sheath. U.S. Pat. No. 5,098,392 to Fleischhacker et al.discloses a dilator and sheath assembly, wherein the dilator is attachedto the sheath through a clamp wherein the clamp is part of the dilatorhub. However, this design presents the ability to come unclamped leadingto the dilator backing out of the sheath. U.S. Pat. No. 4,772,266 toGroshong discloses a dilator and sheath assembly, wherein the hubs ofthe dilator and the sheath lock together by means of compression.However, it would be possible for the dilator to back out of the sheathin this configuration if excessive force is exerted on the tip of thedilator.

It would be beneficial to provide a dilator and sheath assembly thatincorporates a stable releasably locking mechanism to prevent thedilator from backing out of the sheath longitudinally during insertionwhich is not prone to coming unlocked or releasing during use. It wouldalso be beneficial for the sheath of the dilator and sheath assembly tohave a means for sealing the passageway to the patient's vessel, therebyrestricting blood loss and reducing the introduction of contaminantsinto the bloodstream. Moreover, it would be beneficial for this type ofmechanism to have handles, which allow the inserting physician to gainleverage in the process of splitting the sheath apart.

BRIEF SUMMARY OF THE INVENTION

Briefly, the present invention provides a releasably locking dilator andsheath assembly and methods for releasing the dilator from the sheathand longitudinally splitting the sheath in the course of inserting acatheter into a desired vessel to be catheterized.

The invention provides a releasably locking dilator and sheath assembly,comprising a dilator and a sheath. The dilator has a distal tip, anelongated dilator stem, a proximal dilator end, and a dilator hubfixedly connected to the proximal dilator end. The dilator hub includesa threaded portion on its distal end. The sheath comprises a distal end,an elongated hollow tubular section, a proximal sheath end, and a sheathhub fixedly connected to the proximal sheath end. The sheath alsocomprises a longitudinal axis extending between the proximal sheath endand the distal sheath end as well as at least one tear seam disposedlongitudinally on the sheath surface. The sheath hub includes a proximalportion, a mating threaded portion at a proximal end thereof and avalve. The threaded portion of the dilator hub and the mating threadedportion of the sheath hub provide a releasably locking engagementbetween the dilator and the sheath. The sheath is sized to frictionallyretain the dilator.

The invention further provides a releasably locking dilator and sheathassembly, wherein the dilator comprises an elongated dilator stem havinga proximal end and a dilator hub fixedly connected to the proximaldilator end. In addition, the sheath comprises an elongated tubularportion having a longitudinal axis, a proximal sheath end a distalsheath end, and a valve located at the proximal sheath end. The tubularportion of the sheath is sized to frictionally retain the dilator stem.The sheath also comprises at least one tear seam extending between theproximal sheath end and the distal sheath end and a sheath hub fixedlyconnected to the proximal sheath end. The dilator and sheath assemblycomprises a means for providing a releasably locking engagement betweenthe distal portion of the sheath hub and the proximal portion of thedilator hub.

The invention further comprises a releasably locking dilator and sheathassembly, wherein the dilator comprises an elongated dilator stem, aproximal dilator end and a dilator hub having a threaded portion on itsdistal end fixedly connected to the proximal dilator end. The sheathincludes an elongated tubular portion having a proximal sheath end, adistal sheath end and a longitudinal axis extending between the proximalsheath end and the distal sheath end. The assembly includes a valvedisposed at the proximal sheath end. The sheath further comprises twotear seams extending along the tubular portion between the proximalsheath end and the distal sheath end, wherein the two tear seams arelocated on opposite sides of the sheath and are coplanar with thelongitudinal axis of the sheath. The sheath further comprises a firstand second sheath hub portions, each of which comprise an invertedsemicircular edge fixedly connected to the sheath. The first and secondsheath hub portions generally encircle the tubular sheath, with spacesbetween the first and second sheath hub portions. The first and secondsheath hub portions comprise a first and second threaded portion,respectively, at a proximal end thereof. The first and second threadedportions combined comprise a circular threaded portion forming theproximal end of the sheath which is matable with the threaded portion ofthe dilator hub to provide a releasably locking engagement between thedilator and the sheath.

The invention further provides a method of separating a dilator from asheath. The method includes providing a dilator having a dilator stemextending along a longitudinal axis and a dilator hub connected to aproximal end of the dilator stem, wherein the dilator hub comprises amale threaded portion. The method also includes providing a sheathhaving a sheath hub comprising a valve, a female threaded portion andwinged tabs having a perpendicular portion and an angular portionwhereby the dilator is releasably connected to a sheath by mating thethreads on the dilator hub to the threads on the sheath hub. The methodfurther comprises rotating the dilator around the longitudinal axis inrelation to the sheath, thereby unthreading the dilator and the sheathand disengaging the sheath.

The invention further comprises a method of removing a sheath fromaround a catheter assembly, wherein the catheter assembly and sheath areboth partially disposed inside of a desired vessel to be catheterized.The sheath includes a longitudinal axis, a distal portion having adistal tip with a hollow portion aligned with the longitudinal axis ofthe sheath, an elongated tubular structure comprising a hollowpassageway traversing the entire longitudinal axis of the sheath, aproximal portion having a proximal tip at its proximal end, a hollowpassageway along the longitudinal axis of the sheath, and two opposingtear seams running the entire length of the sheath and coplanar with thelongitudinal axis of the sheath. The sheath also includes a sheath hubfixedly connected to the proximal portion of the sheath. The sheath hubcomprises a valve disposed at a proximal end of the sheath and twoopposing reveals which run parallel to the longitudinal axis of thetubular sheath and are coplanar with the tear seams running along thesurface of the sheath and the longitudinal axis of the sheath. Thesheath hub also includes two opposing winged tabs; each tab includes aperpendicular portion and an angled portion. The perpendicular portionextends laterally from the sheath hub in a plane which is perpendicularto the plane containing the longitudinal axis of the sheath and the twoopposing reveals. The angled portion of the tab extends from theperpendicular portion, wherein an angle between the proximal surface ofthe perpendicular portion and the angled portion is between 90° and179°. The method further comprises applying a distal force to theproximal surface of the angled portion of each of the winged tabs;applying a proximal force to the distal surface of each of the tabs at apoint on the tab closer to the center of the sheath than the point uponwhich the distal force is applied to the proximal surface; and graspingthe tabs of the sheath and pulling them outward from the center of thesheath, thereby separating the sheath into two halves along the tearseams running the length of the sheath; and pulling the sheath in theproximal direction.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitutepart of this specification, illustrate the presently preferredembodiments of the invention, and, together with the general descriptiongiven above and the detailed description given below, serve to explainthe features of the invention. In the drawings:

FIG. 1 is a perspective view of a releasably locking dilator and sheathassembly in a locked state in accordance with an embodiment of thepresent invention.

FIG. 2 is a perspective view of the sheath only, from FIG. 1.

FIG. 3 is an enlarged top plan view, in cross-section, of the proximalend of the releasably locking dilator and sheath assembly in a releasedstate.

FIG. 4 is a perspective view of the dilator only, from FIG. 1.

FIG. 5 is a perspective view of a portion of a sheath in accordance withan alternate embodiment of the present invention.

FIG. 6 is a flowchart describing the procedure of catheter insertionutilizing the present invention.

FIG. 7 is a diagram showing a preferable force application used tolongitudinally split the sheath upon removal.

FIG. 8 is a perspective view of a portion of a sheath, in accordancewith an alternate embodiment of the present invention.

FIG. 8 a is a cross-sectional view of the portion of a sheath shown inFIG. 8.

FIG. 9 is a cross-sectional view of a portion of a sheath, in accordancewith an alternate embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings, like numerals indicate like elements throughout.Certain terminology is used herein for convenience only and is not to betaken as a limitation on the present invention. The terms “distal” and“proximal” refer to the directions “away from” and “closer to,”respectively, the body of the physician inserting the dilator and sheathassembly into a patient. The terminology includes the words abovespecifically mentioned, derivatives thereof, and words of similarimport.

The following describes a preferred embodiment of the present invention.However, it should be understood, based on this disclosure, that theinvention is not limited by the preferred embodiment described herein.Referring now to the drawings in detail, there is shown in FIG. 1, anembodiment of a releasably locking dilator and sheath assembly 10. Asshown in throughout, the assembly includes a dilator 12 and a sheath 14,which are releasably locked to each other. The dilator 12 is longer thanthe sheath 14 so that the dilator 12, in the releasably locked positionwith the sheath 14, as shown in FIG. 1, passes through the sheath 14 sothat a distal tip 36 of the dilator 12 extends beyond the distal end 56of the sheath 14.

The sheath 14, as shown in FIG. 2, is a device used to aid in theinsertion of a catheter (not shown) into a vessel (not shown) to becatheterized, as is well known in the art. Since the sheath 14 isgenerally more rigid than a catheter, the sheath 14 can be maneuveredinto place with less effort and trauma to the patient than a catheter.The catheter is then inserted into the vessel through the sheath 14.Once the catheter is in place, the sheath 14 may be removed, therebyleaving the catheter in its desired position. If the catheter has anyencumbrance, such as a hub, on its proximal end, the sheath 14 will haveto be split in order to remove it from the patient's body while leavingthe catheter in place.

The sheath 14 includes a distal end 54 having a tapered distal tip 56,an elongated tubular portion 43, and proximal end containing a sheathhub 40. At least one tear seam 58 is longitudinally disposed along theentire length of the sheath 14. In this preferred embodiment, two tearseams 58 are present. These tear seams 58 are located on opposite sidesof the sheath 14 so that a plane “P” containing the two tear seams 58bisects the sheath 14 longitudinally. The plane “P” contains thelongitudinal axis “L”, as shown in FIG. 3, and extends from the line “L”perpendicular to the surface of the paper.

Referring to FIGS. 2 and 3, two diametrically opposed reveals 48 arelocated on the sheath hub 40, along the tubular portion of the hub. Eachreveal 48 is preferably aligned with one of the tear seams 58 of thesheath 14, so that the reveals 48 and the tear seams 58 are coplanar. Atleast one webbing member 49 is shown and optionally such a webbingmember 49 may be disposed on both sides of sheath hub 40 at the proximalends of reveals 48. The sheath hub 40 is fixedly connected to theproximal end 52 of the sheath 14 such as by an adhesive, ultrasonicbonding, insert molding or another method known to those skilled in theart. The longitudinal axis “L” extends through the sheath 14 and thesheath hub 40. The sheath hub 40 includes an elongated tubular portionsurrounding a portion of the proximal end of the sheath, and first andsecond diametrically opposed winged tabs 42 extending from the sheathhub adjacent its proximal end; the first and second tabs 42 each includea perpendicular portion 44, perpendicular to the longitudinal axis “L”of the sheath 14, and an angled portion 46. The winged tabs 42 extendaway from the plane that contains the diametrically opposed reveals 48of the hub 40 and the tear seams 58 of the sheath 14. As shown in FIG.3, an angle “β” extends between the proximal surface of theperpendicular portion 44 and the angled portion 46 of each of the wings42. The angle “A” ranges from approximately 90° to approximately 179°.Preferably, the angle “β” is between approximately 130° to approximately140°; however, those skilled in the art will recognize that the angle“β” can have other ranges as well. The angled portions 46 of the wingedtabs 42 include raised ridges 47 on their proximal surface to aid ingripping the tabs 46. Alternatively, other raised features on the wingedtabs 42, such as bumps or a crosshatched pattern (not shown) may alsoassist the gripping the winged tabs 42.

As best seen in FIG. 3, the sheath hub 40 is fixedly connected to theproximal end 52 of the sheath 14 such that the exterior of the tubularportion 43 of the sheath 14 is fixedly connected to a portion of theinside of the sheath hub 40. Referring back to FIG. 2, the sheath hub 40has an opening 51 and a top surface 50, which is generally flush aroundthe entire circumference of the opening 51. The flush top surface 50assists in preventing blood loss when the dilator 12 is removed from thesheath 14. The inserting physician may utilize the top surface 50 toprevent blood loss by placing a thumb over the entire opening 51 in theproximal end of the sheath hub 40, as is commonly done in the art. Theopening 51 in the proximal end of the sheath hub 40 also serves as aproximal end to the sheath tubing 43. The part of the inner portion ofthe sheath hub 40 not fixedly connected to the sheath 14, may containfeatures that serve to mate the sheath 14 to the dilator 12 and form areleasably locking connection. The present embodiment shows a part ofinner portion of the sheath hub 40 having female threads 53.

Referring to FIG. 4, the dilator 12 is an elongated device that includesa proximal end 28, a distal end 32 and a stem 26 extending between theproximal end 28 and the distal end 32. At the distal end 32 of thedilator stem 26, a transition portion 34 reduces in diameter to aconically shaped distal tip 36. When in a releasably connected statewith the dilator 12 inside of the sheath 14, the dilator 12 and sheath14 share the same longitudinal axis “L”. The exterior diameter of thestem 26 of the dilator 12 is sized to allow a slight frictionalengagement between the inside of the sheath 14 and the outside of thedilator 12. This frictional engagement will serve to form a seal betweenthe dilator 12 and the sheath 14 and reduce or prevent blood seepagethrough the sheath 14 while the dilator 12 and sheath 14 are releasablyconnected. Preferably, the dilator 12 includes a hollow passageway 31along the length of the dilator 12 from the distal tip 36 to theproximal end of the dilator hub 23. The hollow passageway 31 allows thedilator 12 to be inserted over a guidewire (not shown) and follow theguidewire to the desired position inside the vessel to be catheterized.

The proximal end 28 of the dilator 12 comprises a dilator hub 20 fixedlyconnected to the dilator 12 such as by an adhesive, ultrasonic bonding,insert molding or another method known to those skilled in the art. Thedilator hub 20 includes a proximal end 23 having a male threaded portion25, and at its distal end a lip 22 having a bottom face 24. The threadedportion 25 of the proximal end 23 of the dilator 12 may be used as atemporary fitting for any apparatus (not shown) that may be required tobe attached to the dilator 12. The bottom face 24 is flush around itscircumference. A distal portion 29 of the dilator hub 20 also includesexternal male threads 30 that are located between the lip 22 and thestem 26.

The sheath 14 is preferably constructed of high-density polyethylene,low-density polyethylene or polytetrafluoroethylene. The sheath hub 40is preferably constructed of high-density polyethylene or polypropylene.The dilator is preferably constructed of high-density polyethylene,low-density polyethylene or polypropylene. The dilator hub is preferablyconstructed of high-density polyethylene or polypropylene.

Referring to FIG. 1, the dilator and sheath assembly 10 comprises thedilator 12 and the sheath 14 wherein the dilator 12 and sheath 14 arereleasably locked to each other. When in the releasably locked position,the dilator 12 is positioned inside of the sheath 14 so that the distaltip 36 of the dilator protrudes from the distal end 56 of the sheath 14.Referring back to FIG. 3, the male threads 30 of the dilator hub 20 areengagable with the female threads 53 of the sheath hub 40. Thereleasably locking engagement between the dilator 12 and the sheath 14further serves to prevent blood from flowing between the dilator 12 andthe sheath 14. In the preferred embodiment, the external male threads 30on the dilator hub 20 are engagable with the female threads 53 on thesheath hub 40 for approximately one-quarter turn)(90° in the clockwisedirection about the longitudinal axis “L” of the dilator 12. However,those skilled in the art will recognize that the engagement between thedilator 12 and the sheath 14 may take any number of turns in either theclockwise or counter-clockwise direction.

The female threaded portion 53 of the sheath hub 40 may also be mated toa capping device (not shown) to prevent blood loss through the sheath 14while not requiring the inserting physician to apply his or her thumb toblock the opening 51 in the top flush surface 50 during the periodbetween removal of the dilator 12 and the insertion of the catheter intothe sheath 14. If the transition time is short, the use of the thumb ispreferred, but if there were some delay between the removal of thedilator 12 and the insertion of the catheter, a capping device wouldallow the inserting physician to reduce blood loss and contaminationthrough the sheath 14. With this configuration the capping deviceutilizes the female threaded 53 portion on the sheath hub 14 and isreleasably lockable and unlockable using the same unlocking processutilized in removing the dilator 12.

One alternate embodiment of a sheath hub 140, as shown in FIG. 5, is ahub 140 comprising two separate hub portions 145, 148 fixedly connectedto the sheath 14, wherein each of a first hub portion 145 and second hubportion 148 is connected to the other by one or more webbings 149. Thereare spaces 141 between the hub portions 145, 148. These spaces 141 arespanned by the webbings 149 that connect the first and second hubportions 145, 148. The two hub portions 145, 148, when connected by thewebbings 149 and bonded to the sheath 14, serve as a singular sheath hub140. When combined, the two hub portions 145, 148 have all of thefeatures that the sheath hub 40 (FIG. 3) comprises, including areleasably locking mechanism to mate to the counterpart located on thedilator 12, and a flush top surface 150 to assist in the prevention ofblood loss through the sheath 14. The webbing 149 that connects the twohub portions 145 may be located in one or more places between the twoportions of the sheath hub 140. The webbing 149 and the spaces 141between the two hub portions 145 of the sheath hub 140 are disposed inthe same plane that contains the one or more tear seams 58 along thesheath 14. The features of the sheath hub 140 are virtually identical tothose mentioned in the paragraphs above, with respect to the sheath hub40, with one notable difference being that there are small spaces 141between the two hub portions 145, 148 of the sheath hub 140 and webbing149 connecting those portions. The two hub portions 145, 148 havegenerally semicircular inner surfaces and, when the two hub portions145, 148 are fixedly connected to the sheath 14, the two hub portions145, 148 are the functional equivalent of the flush surface 50 and thefemale threaded portion 53 included in the hub 40 (FIG. 3). The two hubportions 145, 148 also serve as the proximal end 52 of the sheath 14.The space 141 replaces the opposing reveals 48 as a weak point in thesheath hub 40, which assists in splitting the sheath hub 40. The webbing149 connecting the two hub portions 145, 148 has strength less than thatof the rest of the sheath hub 140. This localized decrease in strengthallows for splitting of the sheath hub 140 into two separate sheath hubportions 145, 148. The webbing 149 is disposed along a proximal opening151 so that a flush top surface 150 is intact. This sheath hub 140configuration can be manufactured utilizing a unitary construction.

A preferred method for using the dilator and sheath assembly 10 will nowbe described. The method will be described with reference to the dilatorand sheath assembly 10 as described above, however, it should beunderstood that alternative devices described above or which are capableof accomplishing the same steps may also be used. As shown in FIG. 1,the dilator and sheath assembly 10 has an original configuration,wherein the dilator 12 is disposed inside of the sheath 14 and thedilator 12 and sheath 14 are releasably locked to each other. In thisposition, the distal tip 36 of the dilator 12 protrudes from the distalend 33 of the sheath 14. Also, in this position, the dilator 12 andsheath 14 are releasably locked by the male threads 30 and femalethreads 53 disposed on the dilator hub 20 and sheath hub 40respectively.

Referring to the flowchart of FIG. 6, during insertion of a catheterinto the patient, the dilator and sheath assembly 10 is inserted into avessel to be catheterized (not shown) so that the distal tip 36 of thedilator 12 is in the area to be catheterized. This is done by firstprobing the area to be catheterized to find the desired vessel. Next, inaccordance with the Seldinger technique, an incision is made near thevessel and a thin, hollow tipped needle (not shown) is inserted throughthe incision and into the vessel to be catheterized. Once the hollow tipof the needle is in the vessel to be catheterized, a thin guidewire (notshown) is passed through the needle into the vessel. The guidewire isinserted into the vessel so that the distal end of the guidewire is nearthe desired location to be catheterized. With the guidewire in place,the needle is removed. The dilator and sheath assembly 10 is insertedover the guidewire, with the guidewire being inserted through the hollowpassageway 31 of the dilator 12. In this procedure, the proximal end ofthe guidewire is inserted into the hollow passageway 31, beginning inthe distal tip 36 of the dilator 12, and the dilator and sheath assembly10 is slid along the guidewire in a distal direction until the distaltip 36 of the dilator 12 is in the area to be catheterized. With thedilator and sheath assembly 10 in place, the guidewire is removed bypulling the guidewire in a proximal direction through the dilator 12 andleaving the dilator and sheath assembly 10 in place.

Once the dilator and sheath assembly 10 is in place, the dilator 12 isremoved from the sheath 14. The dilator 12 is rotated around itslongitudinal axis in a counterclockwise direction in relation to thesheath 14 until the dilator 12 is released from the sheath 14. Thedilator 12 is then released from the sheath 14 when the male threads 30of the dilator hub 20 are no longer engaged to the female threads 53 ofthe sheath hub 40. Once the dilator 12 is released from the sheath 14,the dilator 12 is pulled in a proximal direction in relation to thesheath 14 until the distal tip 36 of the dilator 12 is clear of the topflush surface 50 of the proximal end 52 of the sheath hub 40. With thedilator 12 clear of the sheath 14, there is now a hollow passagewaythrough the sheath 14. In the preferred embodiment, the dilator 12 isrotated approximately 90° in relation to the sheath 14 to release theengagement between the dilator 12 and the sheath 14.

However, if there is an alternative releasably locking device existingin place of the male threads 30 and female threads 53 on the dilator 12and sheath 14, respectively, the dilator 12 may be released from thesheath 14 using the appropriate method. These alternative methodsinclude but are not limited to snap fit, screw fit, press fit andlocking tabs.

Once the dilator 12 is removed from the sheath 14, leaving a hollowpassageway through the sheath 14, a catheter (not shown) may be insertedthrough the sheath 14 into the desired vessel to be catheterized. Thedistal tip of the catheter is inserted into the proximal opening 51 ofthe sheath 14 and the catheter is slid distally through the sheath 14until the distal tip of the catheter is in the desired location insideof the vessel to be catheterized. To reduce or prevent blood leakagethrough the sheath 14, before the catheter is inserted through thesheath 14, the inserting physician may apply his or her thumb to theflush top surface 50 of the sheath hub 40 to form a seal. Alternatively,the inserting physician may releasably lock a capping device (not shown)into place on the sheath hub 40, utilizing the mating device on thesheath hub 40 and a mating device on the capping device comprising thesame features as the mating device on the dilator 12.

With the catheter in place, the sheath 14 can now be removed, leavingonly the catheter in the vessel to be catheterized. It is common for thecatheter to have some sort of encumbrance such as a hub, an ingrowthcuff, a collar or other fitting in its proximal region that wouldprevent the sheath 14 from simply being slid over the catheter forremoval. The encumbrance could be a cuff, hub, or other fitting. Toaccommodate removal of the sheath 14 over a catheter with suchencumbrances, the sheath 14 may be split longitudinally. The preferredmethod of removing the sheath 14 according to the present invention isto split the sheath 14 along its longitudinal axis “L” while pulling thesheath 14 proximally out of the patient. The sheath 14 and the sheathhub 40 are split longitudinally into two approximate halves. This methodutilizes the tear seams 58 along the sheath 14 and the two opposingreveals 48 located on the sheath hub 40.

Referring to FIG. 7, the sheath 14 is split by grasping the two wingedtabs 42 and applying a downward or distal force F_(d1), F_(d2) to theproximal or top surface of the angled portion 46 of each of the wingedtabs 42 while applying a proximal force F_(p1), F_(p2) to the distalsurface of each of the winged tabs 42 at a place on each tab that iscloser to the longitudinal axis “L” of the sheath 14 than the point oneach winged tab 42 where the downward force is applied. Preferably, theinserting physician will grasp the tabs 42 by placing his or her thumbon the top of the angled portion 46 of each winged tab 42 and slidinghis or her index finger under each tab 42. The distal force F_(d1),F_(d2) is applied with the inserting physician's thumbs and the proximalforce F_(p1), F_(p2) is applied with the inserting physician's indexfinger. This application of conflicting forces F_(d1), F_(d2) andF_(p1), F_(p2) in strategic positions creates a couple which utilizesthe winged tab 42 design of the present invention to assist theinserting physician in splitting the sheath hub 40 and the sheath 14.The inserting physician creates moments around two points, which arelocated directly between the application points of the distal andproximal forces F_(d1), F_(d2) and F_(p1), F_(p2), thereby creating arotation of the winged tabs 42 along lines R₁ and R₂ which forces thesheath hub 40 to split in the along the plane containing the opposingreveals 48 of the sheath hub 40 and the tear seams 58 of the sheath 14.Essentially, the winged tabs 42 of the sheath hub 40 are used as leversthat pull apart and upward (proximally) on the center of the sheath hub40. This is accomplished by using the point where the proximal forceF_(p1), F_(p2) is applied to the bottom of each winged tab 42 as afulcrum and applying a distal force F_(d1), F_(d2) to a point on theproximal surface of the angled portion 46 of each winged tab 42. Becauseof the two conflicting forces F_(d1), F_(d2) and F_(p1), F_(p2) beingapplied to each of the winged tabs 42, the natural reaction is for thesheath hub 40 to split in the along the plane “P” containing theopposing reveals 48 of the sheath hub 40 and the tear seams 58 of thesheath 14. The splitting of the sheath 14 and the sheath hub 40 allowsthe winged tabs 42 to each rotate about an axis, approximately locatedat A1, A2, created by the conflicting distal and proximal forces F_(d1),F_(d2) and F_(p1), F_(p2) and located between the application points ofthe forces F_(d1), F_(d2) and F_(p1), F_(p2). The approximate directionof rotation is denoted by R1 and R2 in FIG. 7. This design allows theinserting physician to apply distal forces F_(d1), F_(d2) to the outsideof each of the winged tabs 42 and proximal forces F_(p1), F_(p2) atpoints closer to the longitudinal axis “L” of the sheath 14 to achieveresulting proximal and outward forces F_(PO1), F_(PO2) on the center ofthe sheath hub 40.

The angled design of each of the winged tabs 42 greatly improves theleverage that the inserting physician has while working with the sheath14. The angled portion 46 of each of the winged tabs 42 assists theinserting physician in maneuvering the sheath 14 into place. The angledportion 46 of the winged tabs 42 also allows the inserting physician tobe able to reach under each of the tabs 42 with his or her fingers whenthe sheath 14 is completely inserted in the body of the patient therebyallowing the inserting physician to place at least one finger under eachtab 42 to achieve greater leverage in his or her efforts to split thesheath 14 longitudinally in order to withdraw the sheath 14 whileleaving the catheter in place.

This invention is an improvement over the conventional perpendiculartabbed designs because of the leverage that the winged tab 42 designgives the inserting physician during splitting and because the angularportion 46 of the winged tabs 42 allows the inserting physician to placehis or her fingers under the tabs 42 with minimal disturbance to thepatient. The benefit of the lever and fulcrum style winged tabs 42 overconventional perpendicular tabs is a reduction in the required effort tosplit the sheath 14, as well as improved ergonomics and a potentialreduction in trauma to the patient. The design of the present inventionallows the inserting physician to keep his or her hands in a relativelystationary position, in relation to the center of the sheath 14. Thepresent invention allows the inserting physician to split the sheath hub40 by creating the couple on the first and second winged tabs 42 of thesheath hub 40 without pulling the sheath 14 in two different directions.This reduction in outward forces on the sheath 14 greatly reduces thechance that the two halves of the split sheath 14 will stretch theincision made in the flesh of the patient.

Preferably, while applying the forces F_(d1), F_(d2) and F_(p1), F_(p2)necessary to split the sheath 14 as described above, the insertingphysician will also be moving his or her hands in a proximal directionto bring the two approximate halves of the split sheath 14 toward him orherself. This combination of forces will allow the inserting physicianto split the sheath 14 as he or she is pulling it from the patient'sbody, thereby avoiding any encumbrances on the catheter while leavingthe portion of the sheath 14 that is still in the patient's body intact.Gradually as more of the sheath 14 is removed from the patient's body,it is preferable for the inserting physician to move his or her handsslightly away from each other to allow the entire length of the sheath14 to split and avoid any encumbrances on the catheter. This curvilineartranslation of the proximal ends of the two approximate halves,proximally and away from each other, allows the sheath 14 to be slidproximally over the catheter while spreading out enough to clear thecatheter's proximal obstacles. This process best accomplishes the goalof removing the sheath 14 from around the catheter while leaving thecatheter in place when all of the steps mentioned, from grasping thewinged tabs 42 of the sheath hub 40 to pulling the tabs 42 away fromeach other, are done simultaneously in a fluid motion so as to smoothlyremove the sheath 14 from around the catheter. Once the sheath 14 is inplace and the catheter is removed, the incision is then closed aroundthe catheter according to procedures known to those skilled in the art.

An alternative sheath assembly 200 of the present invention, having avalve 260 located at a proximal end 252 of a sheath 214, is shown inFIGS. 8 and 8 a. The valve 260 is preferably shaped in the form of adisc having a diameter that is generally similar to the cross-sectionaldiameter of the sheath 214. The valve 260 has a longitudinal slit 262that facilitates the insertion of objects such as a dilator, catheter orsyringe (not shown) through the sheath 214 while closing when theinserted object is removed. The valve 260 also seals around the insertedobject to prevent blood loss, contamination or the introduction of airinto the bloodstream while an object such as a guidewire, dilator orcatheter is inserted through the sheath 214. Although the opening in thevalve 260 shown in this embodiment is a slit 262, it is known to thoseskilled in the art that the opening in the valve 260 may be of any shapethat will accommodate the insertion of objects such as a dilator,catheter or syringe (not shown) therethrough, such as a cross, or anintersection of any number of slits that share a common center which ispreferably aligned with the longitudinal axis of the sheath 214.Preferably, the valve 260 is constructed of silicone, however, thoseskilled in the art will recognize that the valve 260 may be constructedout of any material that is sufficiently resilient to accommodate theobjects inserted therethrough and return to a closed position.

The valve 260 is located at the proximal end 252 of the sheath 214 andis preferably held into place by being bonded to the sheath hub 240 orsecured by a cap 264. While FIG. 8. shows a valve 260 that is securedinto place by a cap, those skilled in the art will recognize that thevalve may be secured directly to the sheath 214 or the sheath hub 240.The cap 264 is preferably constructed of the same material as the sheathhub 240 and fixedly attached to the sheath hub 240 through ultrasonicwelding or other suitable means. The cap 264 may also be snap fit ontothe hub 240. While FIG. 8 shows a cap 264 that is one piece, thoseskilled in the art will recognize that the cap 264 may be constructedusing more than one piece.

The sheath 214 is generally similar to the sheath 14, described above.Likewise, the sheath hub 240 is generally similar to the sheath hub 40described above. Female threads 253 are located within the sheath hub240 distally of the valve 260, similar to the threads 53 shown in FIGS.2 and 3. A proximal surface 266 of the valve 260 contains a notch 268.The notch 268 crosses the proximal surface 266 and preferably is alignedwith two diametrically opposed reveals 248 located on the sheath hub240. Like the embodiment of a dilator sheath assembly 10 shown in FIGS.1-4, the diametrically opposed reveals 248 shown in FIG. 8 arepreferably aligned with tear seams 258 that run longitudinally along thesheath 214. The cap 264 also contains recesses 270 that are aligned withthe reveals 248 of the sheath hub 240 and the notch 268 of the valve260. Together, the notch 268 of the valve 260, the reveals 248, 270 ofthe sheath hub 240 and the cap 264 and the tear seams 258 of the sheath214 will facilitate the longitudinal splitting of the assembly 200 whenforces are applied to the tabs 246 in the manner described in FIG. 7.

FIG. 9 shows another alternative embodiment of a sheath assembly 300.The assembly 300 of FIG. 9 is similar to the assembly 200 of FIG. 8;however, in the assembly 300 shown in FIG. 9, a valve 360 is locateddistally of female threads 353. In this configuration, the femalethreads 353 are disposed on a cap 364 that is bonded to a sheath hub340. Like the assembly 200, the assembly 300 is also constructed tofacilitate longitudinal splitting when forces are applied to tabs in themanner described in FIG. 7. Referring back to FIG. 9, a notch 368 isdisposed across a proximal surface 366 of the valve 360. The notch 368is aligned with a recess 370 in the cap 364. Although not shown, thenotch 368 and the recess 370 are aligned with reveals and tear seams inthe hub 340 and sheath 314 respectively. The circumferential surface ofthe valve 360 may have retaining grooves 372 notched in the surfacetowards the center of the valve 360. During assembly, the retaininggrooves 372 are aligned with retaining protrusions 374 that extendradially inward from the inner surface of the cap 364.

These and other advantages of the present invention will be apparent tothose skilled in the art from the foregoing specification. Accordingly,it will be recognized by those skilled in the art that changes ormodifications may be made to the above-described embodiments withoutdeparting from the broad inventive concepts of the invention. It shouldtherefore be understood that this invention is not limited to theparticular embodiments described herein, but is intended to include allchanges and modifications that are within the scope and spirit of theinvention as defined in the claims.

What is claimed is:
 1. A dilator and sheath assembly comprising: adilator including an elongated dilator stem having a proximal dilatorend and a dilator hub fixedly connected to the proximal dilator end,wherein the dilator hub includes a locking portion at a distal portionthereof; and a sheath assembly including: an elongated tubular portionhaving a proximal sheath end, a distal sheath end, and a longitudinalaxis extending between the proximal sheath end and the distal sheathend, wherein the tubular portion is sized to receive the dilator stemand includes at least one tear seam extending in a plane between theproximal sheath end and the distal sheath end; a sheath hub fixedlyconnected to the proximal sheath end, wherein the sheath hub includes anelongated tubular portion having a proximal portion defining a proximalopening; a valve positioned in the sheath hub proximal portion andextending across the proximal opening, the valve manufactured from aresilient material; and a cap secured to the sheath hub proximal portionsuch that the cap secures the valve within the sheath hub proximalportion, the cap defining a mating locking portion, wherein the lockingportion of the dilator hub and the mating locking portion of the capprovide a releasably locking engagement between the dilator and thesheath.
 2. The dilator and sheath assembly according to claim 1 whereinthe valve includes a longitudinal slit which extends in the plane of thetear seam.
 3. The dilator and sheath assembly according to claim 1wherein the valve includes a notch extending along one surface thereofand aligned in the plane of the tear seam.
 4. The dilator and sheathassembly according to claim 1 wherein the valve includes one or moreretaining openings which receive projections to retain the valve inposition.
 5. The dilator and sheath assembly according to claim 4wherein the projections extend from the cap.
 6. The dilator and sheathassembly according to claim 1 wherein the sheath tubular portionincludes a pair of opposed tear seams.
 7. The dilator and sheathassembly according to claim 6 wherein the cap is a unitary structurewith a pair of opposed recesses aligned with the tear seams.
 8. Thedilator and sheath assembly according to claim 6 wherein the capincludes two pieces which are separated from one another along a planewhich extends in the plane of the tear seam.
 9. The dilator and sheathassembly according to claim 1 wherein the cap is snap fit onto thesheath hub proximal portion.
 10. The dilator and sheath assemblyaccording to claim 1 wherein the locking portion of the dilator hub is amale thread and the mating locking portion of the cap is a femalethread.
 11. The dilator and sheath assembly according to claim 1 whereinthe dilator hub is rotatable relative to the cap to move between adefined locked position wherein the locking portion of the dilator hubis engaged with the mating locking portion of the cap and a definedunlocked position wherein the locking portion of the dilator hub isdisengaged with the mating locking portion of the cap.
 12. The dilatorand sheath assembly according to claim 11 wherein rotation over a pathof 90° moves the locking portions between the locked position and theunlocked position.